These lamps commonly are delivered ready-for-use. Lamp, Ballast, Reflector, Cable. Accordingly the range of possible problems is marginal.

Issues: When the lamp isn't working:
- screw in tightly
- check cabling
- check wire connectors

Only in very rare cases the lamp is the problem, possibly the starter. If you can hear a click-sound from the ballast this means the ballast is likely to be functional but the lamp not. If both lamp and power socket work it is most likely that the ballast itself is broken.